Very poor performance of JNI AttachCurrentThread on Linux

[Stephan Bergmann]

On 02/27/2013 12:28 AM, Dean Long wrote:
> This function should only get called in debug builds or for the initial
> thread, so I'm guessing
> the app has a custom launcher because, if I'm not mistaken, the default
> launcher creates
> a separate main thread to attach to the JVM while the initial thread waits.

The app in question is LibreOffice, which has an extension mechanism 
(UNO) that allows for extensions in various programming languages, among 
them Java.  For that, it instantiates a JVM in-process and makes JNI 
calls.  Due to the fundamental design of LibreOffice and its extension 
mechanism, it is not practically possible in the general case to either 
prevent such JNI calls from being made on the main thread, nor to 
establish large scopes in which a thread will make JNI calls, to 
restrict Attach/DetachCurrentThread calls to the boundaries of such 
larger scopes.  Therefore, LibreOffice can unfortunately end up making 
rather frequent calls to Attach/DetachCurrentThread from the main thread.

Stephan